Thermal Management System and Method

ABSTRACT

A thermal management system/method allowing efficient electrical/thermal attachment of heat sourcing PCBs to heat sinking PCBs using reflow/wave/hand soldering is disclosed. The disclosed system/method may incorporate a combination of support pins, spacer pads, and/or contact paste that mechanically attaches a heat sourcing PCB (and its associated components) to a heat sinking PCB such that thermal conductivity between the two PCBs can be optimized while simultaneously allowing controlled electrical conductivity between the two PCBs. Controlled electrical isolation between the two PCBs is provided for using spacer pads that may also be thermally conductive. Contact paste incorporated in some embodiments permits enhanced conductivity paths between the heat sourcing PCB, a thermally conductive plate mounted over the heat sourcing PCB, and the heat sinking PCB. The use of self-centering support pins incorporating out-gassing vents in some embodiments allows reflow/wave/hand soldering as desired.

CROSS REFERENCE TO RELATED APPLICATIONS Utility Patent Applications

This patent application is a divisional patent application of parentU.S. Utility Patent Application for THERMAL MANAGEMENT SYSTEM ANDMETHOD, Ser. No. 13/659,066, docket AINNO.0128, filed electronicallywith the USPTO on Oct. 24, 2012 with EFS ID 14062894 and ConfirmationNumber 1046.

Applicants claim benefit pursuant to 35 U.S.C. §120 and herebyincorporates by reference U.S. Utility Patent Application for THERMALMANAGEMENT SYSTEM AND METHOD, Ser. No. 13/659,066, docket AINNO.0128,filed electronically with the USPTO on Oct. 24, 2012 with EFS ID14062894 and Confirmation Number 1046.

The parent U.S. Utility Patent Application for THERMAL MANAGEMENT SYSTEMAND METHOD, Ser. No. 13/659,066, docket AINNO.0128 is acontinuation-in-part (CIP) of parent U.S. Utility Patent Application forIC THERMAL MANAGEMENT SYSTEM, Ser. No. 12/912,476, docket AINNO.0126,filed electronically with the USPTO on Oct. 26, 2010 with EFS ID 8707113and Confirmation Number 2130.

Applicants claim benefit pursuant to 35 U.S.C. §120 and herebyincorporates by reference U.S. Utility Patent Application for IC THERMALMANAGEMENT SYSTEM, Ser. No. 12/912,476, docket AINNO.0126, filedelectronically with the USPTO on Oct. 26, 2010 with EFS ID 8707113 andConfirmation Number 2130.

Provisional Patent Applications

Applicants claim benefit pursuant to 35 U.S.C. §119 and herebyincorporates by reference U.S. Provisional Patent Application forTHERMAL MANAGEMENT SYSTEM AND METHOD, Ser. No. 61/664,940, docketAINNO.0128P, filed electronically with the USPTO on Jun. 27, 2012 withEFS ID 13119127 and Confirmation Number 4912.

PARTIAL WAIVER OF COPYRIGHT

All of the material in this patent application is subject to copyrightprotection under the copyright laws of the United States and of othercountries. As of the first effective filing date of the presentapplication, this material is protected as unpublished material.

However, permission to copy this material is hereby granted to theextent that the copyright owner has no objection to the facsimilereproduction by anyone of the patent documentation or patent disclosure,as it appears in the United States Patent and Trademark Office patentfile or records, but otherwise reserves all copyright rights whatsoever.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

FIELD OF THE INVENTION

The present invention generally relates to thermal management systemsand methods. While not limitive of the invention teachings, the presentinvention may in some circumstances be advantageously applied tosituations where DC-DC power converter modules are mounted to PCBmotherboards using one or more soldering processes. General U.S. patentclassifications that are associated with these application areasgenerally include but are not limited to 363/147; 29/852; 174/266;439/83; and 439/84.

PRIOR ART AND BACKGROUND OF THE INVENTION Overview

The reflow assembly of through-hole power modules is trending towardsreplacement of hand soldering or wave soldering as the preferredassembly technique for many customers in the DC-DC power convertermarket. Hand soldering of through-hole power modules is a slow,manually-intensive process, and requires that both the customer's mainprinted circuit board (PCB) and the DC-DC converter module be pre-heatedin order to solder the through-hole pins to the customer's PCB. Wavesoldering is much quicker, but requires separate equipment, specialmasking fixtures, large amounts of liquid flux, and in most cases acleaning system to remove the flux residues. Additionally, there is alsoa significant amount of hazardous material treatment associated withwave soldering which also adds to the overall expense of the wavesoldering process. Reflow soldering, in contrast, is fully automatic,requires no separate flux or cleaning, produces virtually no hazardouswaste, and is a process which is already being done by many customerboard assemblers as part of their normal fabrication process. All ofthese benefits of reflow soldering significantly reduce the cost ofmounting operations in a production assembly environment.

Through-hole pins are generally preferred in the mounting of DC-DCconverters to motherboard PCBs due to their superior heat and currentcarrying transfer capabilities versus SMT pin mounting configurations.Surface-mountable power modules (that do not use through-hole pins) are,in some applications, a viable alternative to through-hole modules.However, this option does not eliminate problems associated withassembling DC-DC modules with attached thermal base plates. This optionalso drives the cost of DC-DC power modules and the customer's PCBhigher, since more expensive PWB fabrication techniques must be employedto deliver the electrical current from the top mounting layer of thecustomer PCB to the sub-surface thermally conducting layers of the PWBs.

Unfortunately, our present through-hole DC-DC power module designs thatincorporate heat spreader plates (known generally as “base plates”)cannot be reflow assembled. The prior art fails to describe anytechniques and materials that can be used to fabricate base-plated powermodules that can be reflow assembled, while, at the same time, provideother desirable features for the final assembly of modules with thecustomer's main PCB board.

Prior Art Thermal Management Techniques (0100, 0200, 0300)

The prior art teaches several thermal management techniques inconjunction with the implementation of DC-DC converters mounted toprinted circuit boards (PCBs). Several of these implementations includeU.S. Pat. No. 6,545,890 (generally illustrated in FIG. 1 (0100)), U.S.Pat. No. 6,896,526 (generally illustrated in FIG. 2 (0200)), and U.S.Pat. No. 7,085,146 (generally illustrated in FIG. 3 (0300)). All ofthese patents are entitled FLANGED TERMINAL PINS FOR DC/DC CONVERTERSand disclose a DC/DC converter that is mounted to a printed circuitboard with rigid terminal pins which extend into a converter substrateto provide electrical connection to circuitry on the substrate. Aterminal pin includes a flange which abuts the printed circuit board andspaces the converter substrate from the printed circuit board.Connection to the printed circuit board is made by solder providedbetween the flange and the circuit board.

Referencing FIG. 1 (0100), U.S. Pat. No. 6,545,890 details a power boardassembly (0101) incorporating a number of different flange pin styles,one of which is illustrated (0102).

Referencing FIG. 2 (0200), U.S. Pat. No. 6,896,526 details a power boardassembly incorporating a beveled flange pin style (0201), and alsoillustrates how this configuration may be utilized to advantage in awave soldering environment (0202). Note that the beveled edge permitssolder “wicking” on the outer edges of the flange pin at the uppercircuit board surface to promote good electrical and thermalconductivity between the flange pin and the circuit board. Note that theflange pin includes cutouts necessary for out-gassing during the wavesoldering process as shown by the flange pin detail of (0203).

Referencing FIG. 3 (0300) U.S. Pat. No. 7,085,146 details a method ofsoldering flange pins to a PCB main board using solder paste in a reflowprocess. As generally illustrated in FIG. 3 (0300), the process startswith application of solder paste to the PCB (0301) followed by insertionof the flange pin into the PCB (0302) and subsequent reflow soldering ofthe flange pin to the PCB. The pin structures detailed in this patentare generally those detailed in FIG. 2 (0201, 0202) as disclosed in U.S.Pat. No. 6,896,526. While this patent makes use of reflow solderingprocess technology, the wicking features of the flange pin described maynot be sufficient to prevent voids and other structural anomalies fromdegrading the electrical/thermal characteristics of the flange/PCBjunction.

Other prior art PWB connector pin technologies also exist, many of whichincorporate elaborate machined surfaces to accomplish the wickingfunction and support the PWB connector stack. An example of one of thesetechniques is detailed in U.S. Patent Application Publication2010/0122458 that describes a PWB connector pin having an acircularprofile. This particular example includes an unmachined collar having anacircular configuration and side wall that further includes a series ofmachined cylindrical connector shafts formed with the collar along thelongitudinal axis.

Deficiencies in the Prior Art

The prior art as detailed above suffers from the following deficiencies:

-   -   Insufficient Heat Dissipation Capability. In many challenging        high density power conversion systems, the heat dissipation        capability of the power conversion module when used in        conjunction with heat conducting support pins and/or a top heat        sink plate is insufficient. Furthermore, the prior art does not        teach any methodology to improve the heat conduction from the        heat source PCB to a connected heat sink PCB.    -   Thermal Transfer Compound Expansion. Currently available thermal        transfer compound that is deposited (typically by dispensing)        between the base plate and the components/PWB tends to expand        during the reflow solder processing. Once the solder on the        module melts, the expanding thermal transfer compound will        displace the components from their intended positions, in some        cases, moving them so far off their land pads that the unit        becomes inoperable. Thermal pads can be used in place of the        thermal transfer compound, but these pads tend to be more        expensive, are not typically designed to survive reflow assembly        operations, and are thickness-dependent (it most often requires        two or more different pad thicknesses to compensate for the        module's component topology). Another alternative to this        approach would be to use high-temperature solder so that the        components do not reflow during assembly. This approach,        however, requires the components and the PWB to withstand much        higher temperatures (often more than 300° C.), which drastically        increases component cost. Most high-temperature solders also        contain a very high percentage of lead (Pb), which is        problematic from an environmental impact standpoint.    -   Clearance Height Tolerances. The prior art through-hole pins        with shoulders used to connect the power module to the        customer's main board (and to set the height of the power module        above the customer's main board) can be difficult to solder        properly in a reflow assembly process without special relief        and/or venting features added to the pin. These features allow        the flux and solvent vapors to escape and allow the molten        solder a path into the barrel of the pin holes. These features        are generally expensive and make the pins more complicated to        manufacture. Additionally, if the power module PWB and/or the        customer's main board is warped or bowed, the pin shoulders may        not all rest on the main board, producing a possible hot spot if        the pin carries a high current load.    -   Electrical Isolation. PCB Modules, which are mounted directly to        the customer's main board through the use of these shoulder-type        pins, employ the height of the pin shoulders to set the spacing        between the customer's main board and the power module board.        Depending on the lengths of the pin shoulders and variation in        component heights, this may leave some of the components and/or        the ferrite core pairs very close to the customer's main PCB        board. This may result in insulation leakage and/or voltage        isolation issues between the power module component and the main        PCB board.    -   Parts Inventory Issues. The electrical isolation issues detailed        above also require that for every different set of component        heights required, a different pin shoulder length is needed.        This ultimately results in a great number of pins needed to        control the spacing between the components on the power module        and the customer's main board.    -   Component Heat Tolerances. Conventional techniques often place        excessive heat stress on components during the soldering        process.    -   Construction Method Limitations. The prior art often places        limits on construction methods, dual board assemblies, heavy        bottom-side components, etc.    -   Pick-and-Place Assembly. Prior art PCB module configurations are        not suitable for pick-and-place assembly techniques or automated        handling.

While some of the prior art may teach some solutions to several of theseproblems, the core issue of creating a thermal management technique thatis simultaneously compatible with wave/reflow/hand soldering techniquesand also provides for efficient thermal management and robust electricalconductivity between the heat source PCB and the heat sink PCB has yetto be taught by the prior art.

OBJECTIVES OF THE INVENTION

Accordingly, the objectives of the present invention are (among others)to circumvent the deficiencies in the prior art and affect the followingobjectives:

-   -   (1) Provide for a thermal management system and method that is        simultaneously compatible with wave/reflow/hand soldering        techniques.    -   (2) Provide for a thermal management system and method that        provides good thermal conductivity between a heat source PCB and        a heat sink PCB while simultaneously providing high electrical        conductivity between the PCBs.    -   (3) Provide for a thermal management system and method that        provides good thermal conductivity between a heat source PCB and        a heat sink PCB while simultaneously providing controlled        electrical isolation between the PCBs.    -   (4) Provide for a thermal management system and method that        provides good thermal conductivity between a heat source PCB and        a heat sink PCB while simultaneously providing controlled        mechanical isolation between the PCBs.    -   (5) Provide for a thermal management system and method that        provides good thermal conductivity between a heat source PCB and        a heat sink PCB while simultaneously providing minimum heat        source PCB height over the heat sink PCB.    -   (6) Provide for a thermal management system and method that        provides good thermal conductivity between a heat source PCB and        a heat sink PCB while simultaneously allowing for system        reliability in the face of thermal cycle age testing.    -   (7) Provide for a thermal management system and method that        provides for additional dimensions of heat transfer from the        heat source PCB to the heat sink PCB apart from connection pins        or topside heat sinks.

While these objectives should not be understood to limit the teachingsof the present invention, in general, these objectives are achieved inpart or in whole by the disclosed invention that is discussed in thefollowing sections. One skilled in the art will no doubt be able toselect aspects of the present invention as disclosed to affect anycombination of the objectives described above.

BRIEF SUMMARY OF THE INVENTION

A thermal management system/method allowing efficient electrical/thermalattachment of heat sourcing PCBs to heat sinking PCBs usingreflow/wave/hand soldering is disclosed. The disclosed system/method mayincorporate a combination of support pins, spacer pads, and/or contactpaste that mechanically attaches a heat sourcing PCB (and its associatedcomponents) to a heat sinking PCB such that thermal conductivity betweenthe two PCBs can be optimized while simultaneously allowing controlledelectrical conductivity between the two PCBs.

Controlled electrical isolation between the two PCBs is provided forusing spacer pads that may also be thermal conductive. Contact pasteincorporated in some embodiments permits enhanced conductivity pathsbetween the heat sourcing PCB, a thermally conductive plate mounted overthe heat sourcing PCB, and the heat sinking PCB. The use ofself-centering support pins incorporating out-gassing vents in someembodiments allows reflow/wave/hand soldering as desired.

The system/method as disclosed is suitable for any combination ofreflow/wave/hand soldering and thus permits conventional DC-DC powerconversion modules to be assembled to customer PCB main boards usingautomated equipment. The enhanced thermal conductivity inherent in thevarious embodiments of the invention permits automated reflow assemblytechniques to be utilized while maintaining thermal safety margins forcomponents on both the heat sourcing PCB and the heat sinking PCB.Integration of the various thermal conductivity methodologies within asingle thermal management system also permits higher power densities tobe achieved in the heat sourcing PCB, an especially important advantagewhen applied to applications in which the heat sourcing PCB is a DC-DCconverter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the advantages provided by the invention,reference should be made to the following detailed description togetherwith the accompanying drawings wherein:

FIG. 1 illustrates a prior art thermal management system as taught byU.S. Pat. No. 6,545,890;

FIG. 2 illustrates a prior art thermal management system as taught byU.S. Pat. No. 6,896,526;

FIG. 3 illustrates a prior art thermal management system as taught byU.S. Pat. No. 7,085,146;

FIG. 4 illustrates an assembly perspective view of an exemplary systemcontext for a preferred embodiment of the present invention;

FIG. 5 illustrates an exploded perspective assembly view of an exemplaryheat source PCB assembly associated with a preferred embodiment of thepresent invention;

FIG. 6 illustrates a perspective view of an exemplary heat source PCBassembly associated with a preferred embodiment of the presentinvention;

FIG. 7 illustrates a side assembly view of an exemplary heat source PCBassembly associated with a preferred embodiment of the presentinvention;

FIG. 8 illustrates a side assembly view of an exemplary heat source PCBassembly associated with a preferred embodiment of the presentinvention;

FIG. 9 illustrates a perspective view of an exemplary support pin usedin some preferred invention embodiments;

FIG. 10 illustrates a side view of an exemplary support pin used in somepreferred invention embodiments;

FIG. 11 illustrates a top view of an exemplary support pin used in somepreferred invention embodiments that incorporates a 3-channel V-shapedlongitudinal gassing vent;

FIG. 12 illustrates a top view of an exemplary support pin used in somepreferred invention embodiments that incorporates a 3-channel U-shapedlongitudinal gassing vent;

FIG. 13 illustrates a top view of an exemplary support pin used in somepreferred invention embodiments that incorporates a 4-channel V-shapedlongitudinal gassing vent;

FIG. 14 illustrates a top view of an exemplary support pin used in somepreferred invention embodiments that incorporates a 4-channel U-shapedlongitudinal gassing vent;

FIG. 15 illustrates a top view of an exemplary support pin used in somepreferred invention embodiments that incorporates a 4-channelcurve-shaped longitudinal gassing vent;

FIG. 16 illustrates a top view of an exemplary support pin used in somepreferred invention embodiments that incorporates a 4-channel mixed-modeV-shaped/curve-shaped longitudinal gassing vent;

FIG. 17 illustrates a top view of an exemplary support pin used in somepreferred invention embodiments that depicts V-shaped longitudinalgassing vents comprising arbitrary inclusion angles;

FIG. 18 illustrates a side assembly view of an exemplary support pinused in some preferred invention embodiments;

FIG. 19 illustrates a side assembly view of an exemplary support pinused in some preferred invention embodiments in conjunction withinter-board spacing and isolation techniques;

FIG. 20 illustrates a side assembly view of an exemplary support pinused in some preferred invention embodiments depicting “floating” pinplacement;

FIG. 21 illustrates a side assembly view of an exemplary support pinused in some preferred invention embodiments depicting a PWB “floating”pin placement configuration without spacer pads;

FIG. 22 illustrates a side assembly view of an exemplary support pinused in some preferred invention embodiments depicting adjustable PWBspacing using differential though-hole sizing;

FIG. 23 illustrates a side assembly view of an exemplary support pinused in some preferred invention embodiments depicting adjustable PWBspacing using differential spacer pin inclusion angles;

FIG. 24 illustrates an exemplary invention method embodiment flowchart;

FIG. 25 illustrates an exemplary invention method embodiment flowchartdirected to a method of fabricating support pins;

FIG. 26 illustrates an exemplary support pin fabrication step depictingraw material used in support pin fabrication;

FIG. 27 illustrates an exemplary support pin fabrication step depictinginitial turning of the support pin form;

FIG. 28 illustrates an exemplary support pin fabrication step depictingcreation of the venting features within the support pin form;

FIG. 29 illustrates an exemplary support pin fabrication step depictingfinal plating of the support pin form;

FIG. 30 illustrates an exemplary invention method embodiment flowchartdirected to an alternate method of fabricating support pins;

FIG. 31 illustrates an exemplary support pin fabrication step depictingcreation of alternative venting features within the support pin form;

FIG. 32 illustrates an exemplary support pin fabrication step depictingfinal plating of the support pin form;

FIG. 33 illustrates an exemplary invention method embodiment flowchartdirected to an automated lathe-based method of fabricating support pins;

FIG. 34 illustrates an exemplary invention method embodiment flowchartdirected to an automated lathe-based method of fabricating support pins;

FIG. 35 illustrates a side view of a preferred exemplary inventionembodiment in which a bottom-side thermal enhancement plate is utilizedto improve thermal conductivity between the heat source PCB and the heatsink PCB;

FIG. 36 illustrates a perspective assembly view of a preferred exemplaryinvention embodiment in which a bottom-side thermal enhancement plate isutilized to improve thermal conductivity between the heat source PCB andthe heat sink PCB;

FIG. 37 illustrates a perspective assembled bottom-side view of apreferred exemplary invention embodiment in which a bottom-side thermalenhancement plate is utilized to improve thermal conductivity betweenthe heat source PCB and the heat sink PCB;

FIG. 38 illustrates a side view of a preferred exemplary inventionembodiment in which a bottom-side thermal enhancement plate is utilizedto improve thermal conductivity between the heat source PCB and the heatsink PCB having topside conductive traces;

FIG. 39 illustrates a side view of a preferred exemplary inventionembodiment in which a bottom-side thermal enhancement plate is utilizedto improve thermal conductivity between the heat source PCB and the heatsink PCB having buried conductive traces;

FIG. 40 illustrates a system block diagram depicting system embodimentvariations of the present invention and their related heat flows.

DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY EMBODIMENTS

While this invention is susceptible of embodiment in many differentforms, there is shown in the drawings and will herein be described indetailed preferred embodiment of the invention with the understandingthat the present disclosure is to be considered as an exemplification ofthe principles of the invention and is not intended to limit the broadaspect of the invention to the embodiment illustrated.

The numerous innovative teachings of the present application will bedescribed with particular reference to the presently preferredembodiment, wherein these innovative teachings are advantageouslyapplied to the particular problems of a THERMAL MANAGEMENT SYSTEM ANDMETHOD. However, it should be understood that this embodiment is onlyone example of the many advantageous uses of the innovative teachingsherein. In general, statements made in the specification of the presentapplication do not necessarily limit any of the various claimedinventions. Moreover, some statements may apply to some inventivefeatures but not to others.

PCB Not Limitive

The present invention anticipates a wide variety of applicationenvironments in which the disclosed system/method may operate. In manypreferred applications, a heat source PCB is electrically and/orthermally attached to a heat sink PCB. Within this context, the term“printed circuit board”/“printed wiring board” or “PCB”/“PWB” should begiven its broadest possible interpretation to include not onlyconventional printed circuit board technologies but also printed wiringboards and other technologies well known in the art in which electricalconnections are implemented on a fixed or flexible substrate.

DC-DC Converter Not Limitive

The present invention anticipates a wide variety of applicationenvironments in which the disclosed system/method may operate. In manypreferred applications, a heat source PCB assembly comprises a DC-DCconverter subsystem that is electrically and/or thermally attached to aheat sink PCB, often referred to as a customer main board. While this isanticipated as a typical preferred application of the disclosedinvention, the present invention is not limited to this application andmay be applied to a variety of situations where a heat source PCB isconnected to a heat sink PCB with the goal of offloading heat from theheat source PCB (and its associated components) to the heat sink PCB(and its associated components). Within this context the term “DC-DCconverter” and “heat source PCB” are synonymous and the term “mainboard” and “heat sink PCB” are synonymous.

Power Module/Main Board Not Limitive

The present invention anticipates a wide variety of applicationenvironments in which the disclosed system/method may operate. In manypreferred applications, a heat source PCB assembly may comprise a powermodule subsystem that is electrically and/or thermally attached to aheat sink PCB, often referred to as a customer main board. Within thiscontext, the term “power module” and “heat source PCB” are synonymousand the term “main board” and “heat sink PCB” are synonymous.

Heat Source PCB/Heat Sink PCB Not Limitive

References to the surfaces of the heat source PCB and the heat sink PCBfor the purposes of heat transfer dynamics, using contact paste andphase change material as described herein, may include the componentsplaced on the surface of the heat source PCB and the heat sink PCB.

Heat Source PCB/Heat Sink PCB Not Limitive

The present invention anticipates many configurations in which the heatsource PCB is the dominant heat generator when mated with acorresponding heat sink PCB. However, the invention as disclosed issymmetric and in some circumstances the heat source PCB may actually actas a thermal sink to the heat sink PCB. In this context, the heat sinkPCB may actually be the dominant heat generator or operate at the sametemperature as the heat source PCB.

Thermally Conductive Plate Not Limitive

The present invention anticipates a wide variety of configurations inwhich a thermally conductive plate is attached to or mated with a heatsource PCB in order to remove heat from the heat source PCB. Thisthermally conductive plate may be equivalently referred to as a heatsink, heat plate, base plate, etc. with no loss of generality in theteachings of the invention. Within this context, these terms should begenerically identified as any heat sinking mechanism that is attached toor mated with the heat source PCB in these configurations. Note that theuse of the disclosed pliable thermal contact paste may in somecircumstances obviate the need for screw fasteners between the thermallyconductive plate and the heat source PCB. One skilled in the art willrecognize that there are a wide variety of methodologies available toconnect the thermally conductive plate and the heat source PCB withinthis context.

Thermal Enhancement Plate Not Limitive

The present invention anticipates that the use of a thermal enhancementplate as depicted herein between the heat source PCB and the heat sinkPCB may incorporate a wide variety of solid materials, including thosethat are thermally conductive but which may in some circumstances beelectrically insulating or in others electrically conductive. A widevariety of electrically insulating coverings for this thermalenhancement plate are anticipated to ensure electrical isolation betweenthe heat source PCB and the heat sink PCB.

Heat Sink PCB Surface Not Limitive

The heat sink PCB as depicted herein may include optional topsideinsulating material as depicted herein in a wide variety ofcircumstances to ensure electrical isolation between the heat source PCBand the conductive traces/components on the surface of the heat sinkPCB. While this variant may not be illustrated in every inventionembodiment illustrated herein, it will be assumed that every inventionembodiment may incorporate this as an optional feature.

V-Shaped Angle Not Limitive

Various embodiments of the present invention may utilize V-shapedlongitudinal gassing vents in the support pin structures. These one ormore longitudinal gassing vents may be V-shaped at an angle greater thanzero (0) degrees and less than or equal to 180 degrees with respect tothe longitudinal axis of the cylindrical shaft. In the extreme case ofthe gassing vents being configured at 180 degrees, they are essentiallyflat but are still described herein as V-shaped.

Element Combinations Not Limitive

The present invention may incorporate any combination of elementsdetailed herein, including but not limited to: support pins, contactpaste, spacer pads, thermally conductive plates, and heat source PCBs.The configurations presented herein only represent exemplarycombinations of these system elements.

System Context Overview

The present invention in general provides an integrated solution forthermally enhanced power assemblies that can easily be mounted usingreflow assembly processes. To resolve the issue of reflowability ofmodules with heat spreader plates, the present invention utilizes one ormore of the following thermal management techniques. These may beemployed separately or in any combination.

Thermal Contact Paste

The present invention replaces the commonly used two-part thermaltransfer compound with a one-part, highly compliant material which doesnot set up or harden with either temperature or time. This material,although it may undergo thermal expansion or contraction as itstemperature changes, does not apply any force to the components in whichit comes in contact while the solder joints are molten. This eliminatesthe movement of the components from their designated positions duringreflow assembly. This thermal contact paste material also has similarthermal properties to existing thermal transfer compound so as tomaintain the same thermal performance as that in conventional two-partthermal transfer compound.

Support Pins

The present invention replaces the industry-standard shoulder pins withbeveled or filleted self-centering pins. These pins may or may not haverelief or venting features in them, depending on the application inwhich they are being used.

In a wave solder assembly application, the relief/venting features maybe desirable, since the pin joints in the power module PWB do not reflowduring the mounting. The relief/venting features would then leave open apath for the liquid solder to form a fillet around the pin. In a reflowassembly process, however, the venting features can be removed. The pinswill center themselves in the receiving holes, both horizontally (withinthe receiving hole itself) and vertically (between the two PWBs),especially if spacer pads as described below are simultaneouslyemployed. This “3D” self-centering behavior results from surface tensionbalancing between the forming solder joints on the customer's main PWBand the power module's PCB/PWB. A significant advantage to this approachis that the solder “wetting” of the interface between the shoulder pinand the PCB/PWB will result in lower resistivity in the electricalconnection, higher thermal conductivity, and greater overall mechanicalstrength of the connection between the power module and the main board.

Self-centering, “shoulder-less” pins can also reduce module cost.Because of their simpler design, these pins can be fabricated on alathe, instead of a special screw machine, and can therefore use lessexpensive alloys in their construction (the more involved machining ofthe shoulder pins with venting features require harder alloys, which,for high current applications, can be significantly more expensive).

Spacer Pads

To provide electrical insulation (or isolation) between the power modulePWB and the customer's main PWB and to reduce the number of differentpins required for the different power module variations, the presentinvention may attach spacer pads in multiple (typically three or more)locations to the power module's pin side. These pads can vary inthickness, depending on the height desired, and can be cut or punched towhatever shapes are required. The spacer pads may be mounted to the PWBitself or to one or more of the components' surfaces. The pads are madeof a heat resistant, high temperature material and may beadhesive-backed for easy assembly. In one embodiment of the spacer pads,an electrically insulating, yet thermally conductive material can beselected for the pads. This also allows the spacer pads to function as aconduit for heat transfer. The pads may be rectangular and of uniformsize and thickness, or their shapes and thicknesses can be varied frommodule to module or even on the same module, depending on the componentson which they are mounted. This allows the spacing between thecomponents on the power module and customer's main board to bedetermined by the spacers, and not the pin shoulders, thus reducing thenumber of pin sizes needed, and provides a guaranteed safety clearancefor controlled electrical isolation between the power module and mainboard.

Spacer pads can be made to various thicknesses, and more than onethickness can be used on a given module, depending on the topology ofthe module and the elevation of the surfaces on which the pads rest. Ina convective cooling application, where a finned heat sink is mounted onthe top side of a base plate (heat sink) associated with the powerboard, the spacers can raise the power module off the main board PWB andallow airflow under the power module.

In the case where the power module is used in a conduction coolingapplication where heat is transferred from module to heatsink/chassisabove via thermal material, the thermal material (typically a pad) fillsthe space between the power module and the above heatsink/chassis andserves as a conduit for heat transfer. The pads require some compressionto work effectively. The spacers can be used to finely adjust the powermodule height to compress the thermal pads in critical areas to optimizethe conduction cooling.

The self-centering support pin design described above may work inconjunction with spacer pads, permitting the pins to center themselvesbetween the two PWBs, even if the PWB-to-PWB spacing at each pin site isdifferent (such as would be the case if one or both the PWBs were bowedor warped).

System Context Overview (0400, 0500)

The present invention system context may be broadly described asdepicted in FIG. 4 (0400). In this typical application, a heat sourcePCB (0410) is mated to a heat sink PCB (0420) using one or more supportpins (0411) that are soldered to both PCBs (0410, 0420) usingthrough-hole techniques. Spacer pads (0412) are placed between the heatsource PCB (0410) (and/or components mounted to it) and serve to raisethe heat source PCB (0410) over the heat sink PCB (0420) and thusmaintaining a known clearance between the PCBs (0410, 0420) irrespectiveof the configuration of the support pins (0411). Not shown is thethermal contact paste that may be applied between the heat source PCB(0410) and the heat plate (0414) that serves to transfer heat from theheat source PCB (0410) to the heat plate (0414) and through this entityto the heat sink PCB (0420) through fasteners (0415) or other heatconductive attachment means.

An exploded assembly view of the heat source PCB and heat plate assemblyis generally illustrated in FIG. 5 (0500). The heat plate assembly maytake a wide variety of forms and may include variants as shown thatincorporate top cutouts (0501) to permit convection cooling ofcomponents or forced cooling of components (0502) through these openingsduring the reflow soldering process.

Heat Plate Clearance Using Spacer Pads (0600)

The present invention may utilize spacer pads as generally illustratedin FIG. 6 (0600) to ensure that the combination (0610) of the heatsource PCB (0611)/heat plate (0612) maintains a minimum clearancedistance above the heat sink PCB (not shown). This is accomplished byplacing spacer pads (0613) beneath the fasteners (0614) used to tie theheat source PCB (0611) to the heat plate (0612). Equivalently, thespacers (0613) could be placed beneath portions of the heat plate (0612)that do not contain fasteners (0614) to the heat source PCB (0611). Forexample, it is possible for the heat plate (0612) to have extrusionsthat extend directly to the heat sink PCB (0611) and as such permitscrew attachment of the heat plate directly to the heat sink PCB toaffect better thermal transfer from the heat source PCB to the heat sinkPCB. While this is not specifically illustrated in FIG. 6 (0600), oneskilled in the art would be easily capable of generating such anembodiment variant given this diagram.

Note that within this assembled view, the cavity (0615) between the heatsource PCB (0611) and the heat plate (0612) may be filled with thepliable thermal contact paste as described herein to affect optimalthermal transfer between the heat source PCB (0611) and the heat plate(0612) while maintaining electrical isolation between these two elementsand also ensuring that components placed on the heat source PCB (0611)do not shift/move during reflow soldering processes.

Spacer Pad Variations (0700, 0800)

As generally illustrated in FIG. 7 (0700), the heat source PCB (0710)may be electrically/thermally attached to the heat sink PCB (0720) usingone or more support pins (0711). These support pins (0711) may befabricated with a cylindrical shoulder length that is shorter than thedesired minimum assembly distance between the heat source PCB (0710) andthe heat sink PCB (0720). Also, note that the support pins (0712) neednot be identical in size. Spacer pads (0712) may be used to set theminimum distance between the heat source PCB (0710) and the heat sinkPCB (0720) by fixing a minimum distance between components (0716) on theheat source PCB (0710) and the surface of the heat sink PCB (0720).

Within this context, the use of foam spacer pads (0712) is preferred butnot a requirement. These spacer pads (0712) may be thermally conductiveto aid in the heat conduction from the heat source PCB (0710) to theheat sink PCB (0720), but this feature is not a required characteristicof the spacer pads (0712). Additionally, the spacer pads (0712) may havean adhesive backing on one or more of the pad surfaces, but this featureis not a required characteristic of the spacer pads (0712). This minimumclearance spacing methodology ensures that electrical isolation betweenthe components on the heat source PCB (0710) and the surface (orcomponents) of the heat sink PCB (0720) is maintained.

As generally illustrated in FIG. 8 (0800), the spacer pads (0812) mayhave varying thicknesses, be positioned for direct contact (0822)between the heat source PCB (0810) and the heat sink PCB (0820), bepositioned for contact (0832) between components on the heat sink PCB(0820) and the heat source PCB (0810), or be used to set the spacing(0842) between the heat source PCB (0810), fasteners (0815), and theheat sink PCB (0820).

The spacer pads in some preferred embodiments are constructed of lowelectrical conductivity material and may in some circumstances compriselow electrical conductivity foam as the construction material. Oneskilled in the art will recognize that the spacer pad placement optionsillustrated in FIG. 7 (0700) and FIG. 8 (0800) and materials discussedherein represent only a few of the placement/construction possibilitiesto affect minimum clearance distances between the heat source PCB (0710,0810) and the heat sink PCB (0720, 0820).

Support Pin Description (0900, 1000)

A perspective view of an exemplary support pin is generally illustratedin FIG. 9 (0900). A side view of an exemplary support pin is generallyillustrated in FIG. 10 (1000). The support pins typically comprise a topheat source PCB insertion shaft (1001) further comprising a topregistration chamfer (1002), a bottom heat sink PCB insertion shaft(1003) further comprising a bottom registration chamfer (1004), and acenter support shaft (1005) section further comprising top (1006) andbottom (1007) self-centering inclined peripheral edges, and one or morelongitudinal gassing vents (1008).

Within this context, note that the length of the top heat source PCBinsertion shaft (1001) and the bottom heat sink PCB insertion shaft(1003) may differ, as this may be an application specific modificationto the basic support pin structure to accommodate differing thicknessesof heat source PCBs and/or heat sink PCBs.

Support Pin Gassing Vents (1100)-(1700)

It is instructive to note that the type, spacing, and number oflongitudinal gassing vents may vary by application. For example, FIG. 9(0900) and FIG. 10 (1000) illustrate a preferred embodiment whereinthree gassing vents (1008) are equidistantly positioned around theperiphery of the center support shaft (1005). The present inventionanticipates that these longitudinal gassing vents (1008) may be V-shapedor U-shaped with optimal inclusion angles between 30 and 60 degrees.Furthermore, the spacing angle of these longitudinal gassing vents maybe 120 degrees as generally illustrated in FIG. 11 (1100) or positionedat other preferred spacing angles including but not limited to 45degrees, 90 degrees, 180 degrees, etc.

Examples of variations in the type and spacing of the longitudinalgassing vents are generally illustrated in the top views provided inFIG. 12 (1200), FIG. 13 (1300), FIG. (1400), FIG. 15 (1500), FIG. 16(1600), and FIG. 17 (1700). FIG. 11 (1100) and FIG. 12 (1200) illustratethat the venting ports may vary in number and position around theperiphery of the pin. FIG. 13 (1300) and FIG. 14 (1400) illustrate thatthe venting ports may be U-shaped in construction. FIG. 15 (1500)illustrates that the U-shaped ports may have differing depths. FIG. 16(1600) illustrates that the venting ports may be mixed in constructionwithin the same pin structure. FIG. 17 (1700) illustrates that theV-shaped inclusion angle may vary from greater than zero (0) degrees(1710) to 180 degrees (1720) which represents an essentially flatV-shape.

Support Pin Fabrication

A significant advantage to the construction details for the support pinsas generally depicted in FIG. 9 (0900)-FIG. 17 (1700) is the fact thatall of these support pin configurations can be easily fabricated usingextruded metal that is then turned on an automated CNC lathe (or othermachine tool such as a screw machine) to generate the requiredregistration chamfers and self-centering inclined peripheral edges. Thisis in contrast to the construction methodologies that are used for theprior art as generally illustrated in FIG. 1 (0100) and FIG. 2 (0200,0203). These prior art support pin configurations are not amenable tosuch automated methods of fabrication. Note particularly the top pinview (0203) in FIG. 2 (0200) that indicates a non-planar top surface ofthe pin that cannot be fabricated using traditional lathe turningtechniques, resulting in a significantly increased manufacturing costfor this prior art configuration. Thus, the prior art teaches away fromthe type of cost-effective manufacturing technique that may be utilizedwith the present invention construction.

Support Pin Materials

While the present invention anticipates that a wide range of metals maybe used to fabricate the support pin structures, several metals andalloys are currently considered preferred, including copper, copperalloys, C11000 copper alloy, C11000 half-hard copper alloy,tin-plated-copper, tin-plated-copper-alloy, tin-over-nickel platedC11000 half-hard copper alloy, gold-over-nickel plated C11000 half-hardcopper alloy, copper-tellurium alloy, and brass alloys. A presentlypreferred exemplary pin construction comprises C11000 copper alloy,half-hard, or equivalent with plating comprising 200 microinches of 100%matte tin over 100 microinches minimum of nickel.

Support Pin Assembly View (1800)

As generally illustrated in FIG. 18 (1800), reflow assembly of the heatsource PCB (1810) to the heat sink PCB (1820) using the support pins(1811) permits wicking of the solder to the through-holes in the heatsource PCB (1801) and the heat sink PCB (1802) as supported by theout-gassing port vents (1803) on the center support shaft section of thesupport pin (1811). The out-gassing port vents (1803) in thisconfiguration enable the assembly as shown to provide sufficient solderwicking action for reflow, wave, and hand soldering operations. The topand bottom self-centering inclined peripheral edges on the centersupport shaft section of the support pin (1811) permit the support pinto slide within the through-holes in the heat source PCB (1810) and heatsink PCB (1820) and support varying distances (1804) between these PCBsas determined by the spacing pads (not shown) that have been placedbetween the heat source PCB (1810) and heat sink PCB (1820).

Spacer Pad Floating Alignment (1900, 2000)

As generally illustrated in FIG. 19 (1900), the present invention may beembodied in applications wherein “spacer pads” (1931) or other heightdetermining media are used to space the heat source PCB (1910) from theheat sink PCB (1920) and its components (1932). This technique mayequivalently function to space heat source PCB (1910) components fromthe board surface (or other components fastened to the surface) of theheat sink PCB (1920).

This construction technique permits the support pin (1911) to “float”between the heat source PCB (1910) and the heat sink PCB (1920) withinthe plated-through hole (1932) during the soldering process and as suchallows warpage of either PCB to be accommodated in conjunction withguarantees of minimum board-to-board distances via the use of spacingpads or other gap generation devices. This behavior is depicted in FIG.20 (2000) wherein the board-to-board distance (2001) varies based on anumber of tolerance and manufacturing variables, but the “floating” pinconfiguration still permits solder wicking (2002) to both PCBs eventhough there is not necessarily surface contact between the spacer pinand each PCB via the top and bottom self-centering inclined peripheraledges.

Independent PCB Floating Alignment Overview (2100)

As generally depicted in FIG. 21 (2100), the present invention mayutilize the support pins in conjunction with varying hole size patternsin the PCB/PWB to allow the self-centering support pin to set theboard-to-board distance.

When the pin is placed in the PCB receiving hole in the upper powermodule PWB, the chamfered transition regions of the pin allow the pin tosettle into the hole to a depth that is determined by the hole size andthe chamfer angle. By defining D=hole diameter, S=pin shaft diameter,and A=chamfer angle, then the penetration depth ‘P’, to which the pinwill settle in the PCB receiving hole, is given by the expression

P=0.5*tan(90°−A)*(D−S).

The larger the hole diameter, the deeper the pin will settle into thehole. The pin will make contact with the inner side wall of the hole andnot the flat, plated surface of the power module PWB.

When the power module is mounted onto the customer's PWB, theboard-to-board spacing will also be determined by the customer's boardreceiving hole diameter and the pin transition region chamfer angle,just as above. And, again, the same depth relationship applies.

Variations in PCB Hole Sizing (2200)

As generally illustrated in FIG. 22 (2200), the support pin (2231) maybe utilized in scenarios where the heat source PCB hole size (2212) isdifferent than that of the heat sink PCB hole size (2222) but whereinthe support pin chamfer angles (2213, 2223) vary to permit the distance(2232) from the heat source PCB (2211) to the heat sink PCB (2221) to beadjusted. This variation in chamfer angle (2213, 2223) may also beutilized to adjust the solder wicking characteristics to the support pin(2231) as it relates to the individual heat source PCB (2211) and theheat sink PCB (2221). This exemplary configuration also indicates thatthe insertion shaft sizing (2214, 2224) may vary and be defined by theapplication with variations in this insertion shaft sizing dictated inpart by the requirements for pin “wobble” within the PCB holes as wellas board-to-board registration specifications and pin insertionefficiency.

Variations in Support Pin Angle (2300)

As generally illustrated in FIG. 23 (2300), the support pin (2331) maybe utilized in scenarios where the heat source PCB hole size (2312) isidentical to that of the heat sink PCB hole size (2322) but wherein thesupport pin chamfer angles (2313, 2323) vary to permit the distance(2332) from the heat source PCB (2311) to the heat sink PCB (2321) to beadjusted. This variation in chamfer angle (2313, 2323) may also beutilized to adjust the solder wicking characteristics to the support pin(2331) as it relates to the individual heat source PCB (2311) and theheat sink PCB (2321). This exemplary configuration also indicates thatthe top (2315) and bottom (2325) registration chamfers may vary and bedefined by the application with variations in the registration chamfersdictated in part by the requirements of board-to-board registrationspecifications and pin insertion efficiency.

Configuration Combinations

As mentioned previously, the support pin chamfer angle, support pininsertion sizing, support pin chamfer angle (inclined peripheral edge),and heat source/sink hole sizing may be varied in any combination toaffect the self-centering alignment and board-to-board spacingcharacteristics desired by the particular application. This ability tovary the characteristics of the overall system without the use of othercomponents can in some circumstances significantly improve manufacturingyields and reduce manufacturing costs, while allowing a greater degreeof compatibility between heat source PCB manufacturers (often powersupply converter manufacturers) and their respective customers.

Configuration Advantages

This design approach provides a number of advantages over a prior art“shoulder-type” support pin, including but not limited to:

-   -   Self-centering and alignment that improves centering in the        holes and keeps pins perpendicular to the mounting board for        better overall alignment. This feature helps provide reliable        mating between the upper heat source module and the heat sink        motherboard.    -   Hole size can be used to fine tune spacing between the boards.        It allows a single pin to be used for multiple board spacing        requirements (for example, accommodating different component        heights on bottom of module or fine tuning total module height        for conduction cooling applications), reducing tooling and        inventory costs.    -   Spacing sensitivity to hole size can be adjusted by changing the        chamfer angle between 0 and 90 degrees. A shallow angle allows a        much wider range of adjustment but is more sensitive.    -   Smaller possible annular ring diameters can be used.        Shoulder-type pins require an annular ring surrounding the PWB        receiving hole in order to allow solder fillets to form on the        side of the pin. This annular ring must be larger than the pin's        collar width (the widest part of the pin) to form the fillets.        This uses PWB space, which is always at a premium. With the        self-centering pin approach, the solder fillets can form on the        transition region faces instead of the pin side walls, thus        reducing the required size of the annular rings (it does not        eliminate them, but it does reduce their required diameters).        One skilled in the art will recognize that this list is only        exemplary of the advantages of the present invention as applied        in this context.

System Assembly Overview

While many forms of assembly between the heat source PCB and heat sinkPCB are anticipated, the present invention specifically anticipates a“pin-in-paste” or “pin-in-hole” assembly process to be used in manypreferred embodiments.

In general terms, the “pin-in-paste” or “pin-in-hole” process are fairlysimple and involve the following steps:

-   -   The receiving PWB is printed with solder paste.    -   The power modules and all other components are placed on or in        the PWB.    -   The PWB and components are reflow soldered in an in-line oven.

This general method may be modified heavily depending on a number offactors, with rearrangement and/or addition/deletion of stepsanticipated by the scope of the present invention. Integration of thisand other preferred exemplary embodiment methods in conjunction with avariety of preferred exemplary embodiment systems described herein isanticipated by the overall scope of the present invention.

Specifications for Spacer Pads

While the present invention anticipates that a wide variety of spacerpad materials may be used in construction, some materials are preferred.With respect to the spacer pad materials, the spacer pad may be in somepreferred embodiments source from a “STOCKWELL ELASTOMERICS, INC.”, partnumber “STAND OFF SPACERS.” These spacer embodiments are constructed ofRogers Corporation BISCO HT-6360 Flame Retardant Silicone RubberSheeting, 65 durometer (the HT indicates High Temperature). Thismaterial is then kiss-cut into 0.25″×0.25″ squares, 0.032″ thick, andbacked with an adhesive on one side. The spacer material is typicallyblack and complies with the UL 94V-0 standard.

While this spacer material is not thermally conductive, other equivalentmaterials may be thermally conductive. These may include spacer padsfrom the BERGQUIST COMPANY (18930 West 78th Street, Chanhassen, Minn.55317, (952) 835-2322) under their Part number “Gap Pad 2500S20”. Othersuitable thermal pad materials are available from the BERGQUIST COMPANYunder their SIL-PAD® and POLY-PAD® brands.

Specifications for Thermal Contact Paste

While the present invention anticipates that a wide variety of thermalcontact paste materials may be used in construction, some materials arepreferred. With respect to the thermal contact paste materials, apreferred material is source from the BERGQUIST COMPANY (18930 West 78thStreet, Chanhassen, Minn. 55317, (952) 835-2322) under their part number“LF2000”.

Method Overview (2400)

The present invention system described above may be utilized inconjunction with an assembly method, as generally described in theflowchart illustrated in FIG. 24 (2400). The steps in this thermalmanagement assembly method generally comprise:

-   -   (1) Applying thermal contact paste to the top side of a heat        source PCB (or alternatively, applying thermal contact paste to        the bottom side of a thermal transfer plate) (2401);    -   (2) Attaching a thermal transfer plate to the top of the heat        source PCB (2402);    -   (3) Pre-assembling the heat source PCB with support pins        installed in through-holes in the heat source PCB (2403);    -   (4) Optionally applying spacer pads to the bottom side of the        heat source PCB (or, equivalently, to components placed on the        bottom side of the heat source PCB) (2404);    -   (5) Optionally applying spacer pads to the top side of the heat        sink PCB (or, equivalently, to components placed on the top side        of the heat sink PCB) (2405);    -   (6) Applying solder paste to the top side of the heat sink PCB        (2406);    -   (7) Inserting the support pins attached to the heat source PCB        into the through-holes in the heat sink PCB (2407); and    -   (8) Processing the heat source PCB/heat sink PCB combination        using reflow soldering (2408).

This general method may be modified heavily depending on a number offactors with rearrangement and/or addition/deletion of steps anticipatedby the scope of the present invention. Integration of this and otherpreferred exemplary embodiment methods in conjunction with a variety ofpreferred exemplary embodiment systems described herein is anticipatedby the overall scope of the present invention.

Thermal Cycle Age Testing

The present invention has many preferred application contexts, but oneapplication involves assembly of DC-DC converter modules in environmentswherein the assembled system is subject to high differential thermalcycling. The utilization of the support pins, spacer pads, and contactpaste in this context permits the overall assembled system (heat sourcePCB and heat sink PCB) to be mechanically rigid, yet withstand repeatedthermal cycling. This result is directly related to the high mechanicalstability of the soldered top/bottom self-centering inclined peripheraledges of the support pin center shaft that tend to “wick” solder at thecontact surface of the heat source PCB and heat sink PCB solderingpoints. Additionally, the spacer pads, being comprised of a foammaterial, withstand vibration without inducing component-to-PCB solderfailures that are associated with traditional potting compound and thelike. The contact paste, being pliable and of a non-setting nature,retains its pliability over time and temperature variations and as such“gives” in response to variations in thermal cycling, reducing stress onsurface-mounted components and their associated PCB solder pads.

Given that many applications of the present invention require successfultesting of 700 or more thermal cycles to meet customer reliabilitystandards, the incorporation of the above techniques provides for a veryrobust overall thermal management system/method when applied as taughtherein. This resilience in the face of thermal shock is also anadvantageous characteristic in the application of wave/reflow/handsoldering techniques used to mechanically/electrically attach the heatsource PCB to the heat sink PCB in a modern manufacturing environment.

Support Pin Fabrication (2500, 2600, 2700, 2800, 2900)

The support pins used in various embodiments of the present inventionmay be fabricated in a wide variety of ways. However, in order toachieve economic manufacturing while maintaining optimal solder wickingfeatures, several support pin manufacturing methods are preferred. Asgenerally illustrated in FIG. 25 (2500), a preferred exemplaryfabrication methodology comprises the following steps:

-   -   (1) Begin pin fabrication with a blank wire, whose diameter is        equal to or slightly larger than the widest part of the pin. As        shown in FIG. 26 (2600), the blank is an individual piece, but        this would normally just be a section of a continuous spool of        wire. In high volume applications, the blank wire itself may be        pre-grooved, eliminating the need to make the cuts shown later        in this procedure. (2501);    -   (2) The blank piece of wire is turned on a lathe (or other        machine tool such as a screw machine) to produce the pin shape,        including the beveled collar region (the wide section). As can        be seen in the image depicted in FIG. 27 (2700), this pin form        does not have a shoulder. (2502);    -   (3) Once the pin shape is established, the venting features        (also known as slots or grooves) are cut into the collar section        of the pin to the depth of the pin shaft. As shown in FIG. 28        (2800), the venting grooves extend the entire length of the        collar section. In some invention embodiments, this process may        be one of deformation (as in rotational knurling) rather than        removal of stock material. (2503); and    -   (4) The machined pins are then cleaned and plated with whatever        metal(s) is (are) required, as shown in FIG. 29 (2900). This        plating can comprise Tin, Tin over Nickel, Gold over Nickel, or        a variety of other films. (2504).

This general method may be modified heavily depending on a number offactors with rearrangement and/or addition/deletion of steps anticipatedby the scope of the present invention. Integration of this and otherpreferred exemplary embodiment methods in conjunction with a variety ofpreferred exemplary embodiment systems described herein is anticipatedby the overall scope of the present invention. One skilled in the artwill recognize that this fabrication methodology is only exemplary ofmany possible methods to manufacture the support pins.

Support Pin Alternate Fabrication (3000, 3100, 3200)

The support pins used in various embodiments of the present inventionmay be fabricated in a wide variety of ways. However, in order toachieve economic manufacturing while maintaining optimal solder wickingfeatures, several support pin manufacturing methods are preferred. Asgenerally illustrated in FIG. 30 (3000), a preferred alternatefabrication methodology comprises the following steps:

-   -   (1) Begin pin fabrication with a blank wire, whose diameter is        equal to, or slightly larger than the widest part of the pin. As        shown in FIG. 26 (2600), the blank is an individual piece, but        this would normally just be a section of a continuous spool of        wire. (3001);    -   (2) The blank piece of wire is turned on a lathe (or other        machine tool such as a screw machine) to produce the pin shape,        including the beveled collar region (the wide section). As can        be seen in the image depicted in FIG. 27 (2700), this pin form        does not have a shoulder. (3002);    -   (3) As an alternate machining approach to the full length        grooves shown in FIG. 28 (2800), the venting features need not        extend the entire length of the collar section of the pin. The        venting of the trapped gases during the reflow operations may be        accomplished by cutting the grooves through the beveled sections        only as depicted in FIG. 31 (3100). Although this does result in        less total machining (and less material removal), it may not        reduce the machining costs, as the cutting bit still has to move        across the entire collar section to make the end cuts. In some        invention embodiments, this process may be one of deformation        (as in rotational knurling) rather than removal of stock        material. (3003); and    -   (4) The machined pins are then cleaned and plated with whatever        metal(s) is (are) required, as shown in FIG. 32 (3200). This        plating can comprise Tin, Tin over Nickel, Gold over Nickel, or        a variety of other films. (3004).

This general method may be modified heavily depending on a number offactors with rearrangement and/or addition/deletion of steps anticipatedby the scope of the present invention. Integration of this and otherpreferred exemplary embodiment methods in conjunction with a variety ofpreferred exemplary embodiment systems described herein is anticipatedby the overall scope of the present invention.

Support Pin Lathe Fabrication Techniques (3300, 3400)

The fabrication techniques depicted in FIG. 25 (2500) and FIG. 30 (3000)generally may be implemented using a lathe or other machine tool,implementing a fabrication method as generally depicted in theflowcharts of FIG. 33 (3300) and FIG. 34 (3400) and comprising thefollowing steps:

-   -   (1) The blank wire stock is chucked into the lathe (or other        machine tool such as a screw machine) with a portion        corresponding to the support pin length plus some        parting/supporting excess extending beyond the end of the lathe        chuck. The distal end of this blank wire stock may be supported        by a lathe tailstock. (3301)    -   (2) As the lathe chuck rotates, one or more cutting tools        traverse across the length of the blank wire stock to (a)        dimension the outer diameter of the blank wire stock to the        desired outer pin diameter, (b) form the top and bottom        registration chamfers, and (c) form the top and bottom        self-centering inclined peripheral edges of the support pin.        These operations generate a pre-formed support pin structure.        (3302)    -   (3) The lathe chuck is stopped and rotationally indexed to one        or more rotational positions corresponding to positions in which        the longitudinal gassing vents are to be positioned on the outer        surface of the pre-formed support pin. (3303)    -   (4) A cutting tool is moved longitudinally across the entire        length (as detailed in FIG. 25 (2500)) (or a portion of the        entire length as detailed in FIG. 30 (3000)) of the pre-formed        support pin to form one or more longitudinal gassing vents along        the current rotational index of the pre-formed support pin. This        longitudinal gassing vent generation step may alternatively be        performed in some embodiments using a deformation process (such        as rotational knurling) with a knurling tool or similar        machining deformation process. (3304)    -   (5) The lathe chuck is rotated to the next rotational index and        steps (3) and (4) are repeated for each rotational index in        which a longitudinal gassing vent is to be formed in the        pre-formed support pin. (3305)    -   (6) The pre-formed support pin is parted (cut/removed) from the        remainder of the blank wire stock at the lathe tailstock end of        the blank wire stock (if the blank wire stock is supported by a        lathe tailstock) and at the lathe chuck end of the blank wire        stock. This parting process is normally implemented by rotating        the lathe chuck and using a parting tool to cut through the        desired portions of the blank wire stock. (3306)    -   (7) After the lathe chuck jaws have been released and the end of        the blank wire stock has been extended beyond the end of the        chuck in preparation for a new machining operation, the process        repeats at step (1). (3307)        This general method may be modified heavily depending on a        number of factors with rearrangement and/or addition/deletion of        steps anticipated by the scope of the present invention. The use        of CNC milling or other 4-axis lathe techniques may be        integrated within this methodology. Integration of this and        other preferred exemplary embodiment methods in conjunction with        a variety of preferred exemplary embodiment systems described        herein is anticipated by the overall scope of the present        invention.

These exemplary steps may be used to automate the process of the supportpin manufacture and thus reduce the overall cost of the support pins andimprove their manufacturability. The use of raw blank wire stock sourcedin reel form may in some circumstances permit this process to be totallyautomated if incorporated with an automated feed system and pneumaticchucking system (as may be used with a conventional 5C collet chuck).The use of CNC controls within this overall methodology is anticipatedby the present invention. The automated nature of this support pinfabrication permits a wide variety of “just-in-time” support pinconfigurations to be generated in support of a wide variety ofmotherboard/daughterboard combinations, soldering profiles, andboard-to-board alignment/spacing variations.

Thermal Enhancement Plate (3500, 3600, 3700)

The present invention may incorporate, as an additional feature, athermal enhancement plate, as generally depicted in FIG. 35 (3500), FIG.36 (3600), and FIG. 37 (3700), that is mated to the bottom side of theheat source PCB assembly to permit improved thermal heat transfer fromthe heat source PCB to the heat sink PCB.

As generally illustrated in the side view of FIG. 35 (3500) and theperspective view of FIG. 36 (3600), the heat source PCB (3510, 3610) iselectrically connected to the heat sink PCB (3520) using support pins(3511, 3611) as taught herein. Conductive filler material (thermallyconductive spacer pads and/or contact paste) (3512) is used to thermallylink the heat source PCB (3510) and/or its components to the thermallyconductive plate (3514, 3614). In addition to this heat transfermechanism, a lower thermal enhancement plate (3518, 3618, 3718) mayutilize conductive filler material (thermally conductive spacer padsand/or contact paste) (3512) to thermally link the heat source PCB(3510, 3610) and/or its components to the heat sink PCB (3520) via alayer of phase change material (3519, 3619, 3719). In an exemplaryembodiment, the conductive filler material (3512) is BERGQUIST modelLF2000 and the phase change material (3519, 3619, 3719) is BERGQUISTmodel HF300G.

The thermal enhancement plate (3518, 3618, 3718) is electricallyinsulating, yet thermally conductive, and may be made of metal with aninsulating coating or a ceramic. In certain applications, the thermalenhancement plate (3518, 3618, 3718) may be electrically conductive ifit doesn't contact live metal on either the heat source PCB (3510, 3610)or the heat sink PCB (3520) and if there are no additional isolationrequirements.

The phase change material (3519, 3619, 3719) serves as an interfacebetween the thermal enhancement plate (3518, 3618, 3718) and the heatsink PCB (3520) and may be applied directly to components on the heatsink PCB (3520) as well as the thermal enhancement plate (3518, 3618,3718). The phase change material (3519, 3619, 3719) wets to the heatsink PCB (3520) at a relatively low pressure and temperature to fill anygaps between the thermal enhancement plate (3518, 3618, 3718) and theheat sink PCB (3520).

It should be noted that the use of the thermal enhancement plate (3518,3618, 3718) with or without the use of the phase change material (3519,3619, 3719) may be used to set the spacing distance between the heatsource PCB (3510, 3610) and the heat sink PCB (3520) in the same waythat various embodiments of the support pins and/or spacer padsdescribed herein may be used to set this board-to-board spacingdistance. Thus, the thermal enhancement plate (3518, 3618, 3718), withor without the use of the phase change material (3519, 3619, 3719), maybe used to define the seating plane of the heat source PCB (3510, 3610)with respect to the heat sink PCB (3520).

Thermal Conduction Methodologies (3800, 3900) Thermal Conduction to HeatSink PCB

The present invention promotes a holistic approach to heat transfer fromthe heat source PCB to the heat sink PCB. The basis for heat conductionbetween the heat source PCB and the heat sink PCB is the use ofadditional conduction paths that exhibit greater thermal conductivitythan that provided by simple radiation or ambient air heat transfer. Thefollowing table illustrates the relative thermal conductivities ofvarious materials as compared to ambient air:

Materials K(W/m° K) K(W/in° C.) Copper 355 9 Aluminum 175 4.44 FR4 0.250.0064 Solder 63/67 39 1 Air 0.0275 0.0007The significant fact to be observed from this data is that while atypical heat sink PCB may be constructed of FR4 (which is an electricalinsulator), this material has a thermal conductivity which isapproximately an order of magnitude greater than ambient air. Thus,significant thermal transfer can occur between the thermal enhancementplate and a heat sink PCB constructed of FR4 material, even if there areno copper traces on the surface of the heat sink PCB mating area.

Heat Sink PCB Topside Conductive Traces (3800)

As generally illustrated in FIG. 38 (3800), the use of the thermalenhancement plate (3818) in conjunction with the phase change material(3919) permits heat conduction from the heat source PCB (3810) throughthe contact paste (3812) through the thermal enhancement plate (3818)through the phase change material (3819) to a conductive trace (3821) onthe heat sink PCB (3820). Since the conductive trace is typicallycomprised of copper, heat conduction to the remainder of the heat sinkPCB (3820) is promoted by this configuration.

Note that in this context, an optional insulating material (3822) may beplaced between the phase change material (3819) and the top of the heatsink PCB (3820) conductive trace (3821). This insulating material mayhave many configurations, including but not limited to ceramic, paper,MYLAR®, KAPTON®, FIBERGLASS®, or other known electrically insulatingmaterials. Additionally, in some circumstances the thermal enhancementplate (with or without the optional insulating material (3822)) may beplaced directly on top of the heat sink PCB (3820) with or without theuse of the phase change material (3819).

Heat Sink PCB Internal Conductive Traces (3900)

As generally illustrated in FIG. 39 (3900), the conduction mechanism tothe heat sink PCB (3920) does not necessarily require that theconductive trace (3921) be present on the top of the heat sink PCB(3920). Since the PCB material used for the heat sink PCB (3920) isthermally conductive, it may be used to promote heat conduction throughthe FR4 material at the surface of the PCB to an internal conductivetrace (or power plane) and thus achieve significant improvements inoverall thermal heat transfer from the heat source PCB (3910) to theheat sink PCB (3920).

As generally illustrated in FIG. 39 (3900), the use of the thermalenhancement plate (3918) in conjunction with the phase change material(3919) permits heat conduction from the heat source PCB (3910) throughthe contact paste (3912) through the thermal enhancement plate (3918)through the phase change material (3919) through the insulating topsurface of the heat PCB (3920) to an inner conductive trace (3921)within the heat sink PCB (3920). Since the conductive trace is typicallycomprised of copper, heat conduction to the remainder of the heat sinkPCB (3920) is promoted by this configuration.

Note that in this context, an optional insulating material (3922) may beplaced between the phase change material (3919) and the top of the heatsink PCB (3920) to provide additional electrical isolation to theconductive trace (3921). Additionally, in some circumstances the thermalenhancement plate (with or without the optional insulating material(3922)) may be placed directly on top of the heat sink PCB (3920) withor without the use of the phase change material (3919).

Invention Variants Heat Flow Summary (4000)

A schematic diagram illustrating how heat flows within variouscombinations of various invention embodiments is generally illustratedin FIG. 40 (4000), where the heat source PCB (4010) transfers heat to aheat plate (4014) through thermally conductive filler material (spacerpads or contact paste). Thermal conduction between the heat source PCB(4010) to the heat sink PCB (4020) may occur through support pins(4011), spacer pads (4012), thermal enhancement plate (4018) (with orwithout phase change material (4019) and/or optional electricallyinsulating material (4022)). Any of these thermal contact interfaces maybe optionally optimized via the use of thermal contact paste and/orthermally conductive spacer pads.

System Summary

The present invention system anticipates a wide variety of variations inthe basic theme of construction, but can be generalized as a thermalmanagement system comprising:

-   -   (a) support pin;    -   (b) spacer pad; and    -   (c) contact paste;    -   wherein    -   the support pin comprises metal;    -   the spacer pad comprises low electrical conductivity material;    -   the contact paste comprises a thermally conductive pliable        material that has low electrical conductivity;    -   the support pin comprises a cylindrical shaft further        comprising:        -   (a) top heat source PCB insertion shaft further comprising a            top registration chamfer;        -   (b) bottom heat sink PCB insertion shaft further comprising            a bottom registration chamfer; and        -   (c) center support shaft section further comprising:            -   top and bottom self-centering inclined peripheral edges,                and            -   one or more longitudinal gassing vents;    -   the top and bottom self-centering inclined peripheral edges of        the support pin, when making contact with the surface of a heat        source PCB and a heat sink PCB, create a low electrical        impedance conduction path from the heat source PCB to the heat        sink PCB through the support pin;    -   the top and bottom self-centering inclined peripheral edges of        the support pin, when making contact with the surface of a heat        source PCB and a heat sink PCB, create a low thermal impedance        conduction path from the heat source PCB to the heat sink PCB        through the support pin;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, creates a low thermal        impedance conduction path from the heat source PCB to the heat        sink PCB through the bottom-side and the top-side components        through the spacer pad;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, fixes the minimum        distance between the bottom-side components attached to the heat        source PCB and the top-side components attached to the heat sink        PCB;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, sets the total height        of the heat source PCB above the heat sink PCB; and    -   the contact paste, when making contact with the top-side        components of the heat source PCB and the bottom surface of a        thermally conductive plate covering the heat source PCB, creates        a low thermal impedance conduction path from the top-side        components of the heat source PCB to the thermally conductive        plate covering the heat source PCB through the contact paste.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Contact Paste Alternative System Summary

The present invention as embodied in a contact paste assemblyalternative system anticipates a wide variety of variations in the basictheme of construction but can be generalized as a thermal managementsystem comprising:

-   -   (a) heat source PCB;    -   (b) thermally conductive plate; and    -   (c) contact paste;    -   wherein    -   the contact paste comprises a one-part, pliable, non-curable,        thermally conductive material that has low electrical        conductivity;    -   the contact paste makes contact with the top-side components of        the heat source PCB and the bottom surface of the thermally        conductive plate covering the heat source PCB; and    -   the contact paste creates a low thermal impedance conduction        path from the top-side components of the heat source PCB to the        thermally conductive plate covering the heat source PCB through        the contact paste.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Support Pin Alternative System Summary

The present invention as embodied in a support pin assembly alternativesystem anticipates a wide variety of variations in the basic theme ofconstruction but can be generalized as a thermal management systemcomprising:

-   -   (a) heat source PCB; and    -   (b) support pin;    -   wherein    -   the support pin comprises metal;    -   the support pin comprises a cylindrical shaft further        comprising:        -   (a) top heat source PCB insertion shaft further comprising a            top registration chamfer;        -   (b) bottom heat sink PCB insertion shaft further comprising            a bottom registration chamfer; and        -   (c) center support shaft section further comprising:            -   top and bottom self-centering inclined peripheral edges,                and            -   one or more longitudinal gassing vents;    -   the top and bottom self-centering inclined peripheral edges of        the support pin, when making contact with the surface of the        heat source PCB and a heat sink PCB, create a low electrical        impedance conduction path from the heat source PCB to the heat        sink PCB through the support pin; and    -   the top and bottom self-centering inclined peripheral edges of        the support pin, when making contact with the surface of the        heat source PCB and a heat sink PCB, create a low thermal        impedance conduction path from the heat source PCB to the heat        sink PCB through the support pin.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Support Pin Combined Alternative System Summary

The present invention as embodied in a support pin assembly combinedalternative system anticipates a wide variety of variations in the basictheme of construction, but can be generalized as a thermal managementsystem comprising:

-   -   (a) heat source PCB;    -   (b) thermally conductive plate;    -   (c) support pin; and    -   (d) contact paste;    -   wherein    -   the support pin comprises metal;    -   the support pin comprises a cylindrical shaft further        comprising:        -   (a) top heat source PCB insertion shaft further comprising a            top registration chamfer;        -   (b) bottom heat sink PCB insertion shaft further comprising            a bottom registration chamfer; and        -   (c) center support shaft section further comprising:            -   top and bottom self-centering inclined peripheral edges,                and            -   one or more longitudinal gassing vents;    -   the top and bottom self-centering inclined peripheral edges of        the support pin, when making contact with the surface of the        heat source PCB and a heat sink PCB, create a low thermal        impedance conduction path from the heat source PCB to the heat        sink PCB through the support pin;    -   the contact paste comprises a one-part, pliable, non-curable,        thermally conductive material that has low electrical        conductivity;    -   the contact paste makes contact with the top-side components of        the heat source PCB and the bottom surface of the thermally        conductive plate covering the heat source PCB; and    -   the contact paste creates a low thermal impedance conduction        path from the top-side components of the heat source PCB to the        thermally conductive plate covering the heat source PCB through        the contact paste.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Spacer Pad Alternative System Summary

The present invention as embodied in a spacer pad assembly alternativesystem anticipates a wide variety of variations in the basic theme ofconstruction but can be generalized as a thermal management systemcomprising:

-   -   (a) heat source PCB;    -   (b) thermally conductive plate;    -   (c) spacer pad; and    -   (d) contact paste;    -   wherein    -   the spacer pad comprises low electrical conductivity material;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, creates a low thermal        impedance conduction path from the heat source PCB to the heat        sink PCB through the bottom-side and the top-side components        through the spacer pad;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, fixes the minimum        distance between the bottom-side components attached to the heat        source PCB and the top-side components attached to the heat sink        PCB;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, sets the total height        of the heat source PCB above the heat sink PCB;    -   the contact paste comprises a one-part, pliable, non-curable,        thermally conductive material that has low electrical        conductivity;    -   the contact paste makes contact with the top-side components of        the heat source PCB and the bottom surface of the thermally        conductive plate covering the heat source PCB; and    -   the contact paste creates a low thermal impedance conduction        path from the top-side components of the heat source PCB to the        thermally conductive plate covering the heat source PCB through        the contact paste.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Thermal Enhancement Plate Combined System Summary

The present invention as embodied in a thermal enhancement plateassembly combined system anticipates a wide variety of variations in thebasic theme of construction but can be generalized as a thermalmanagement system comprising:

-   -   (a) heat source PCB;    -   (b) thermal enhancement plate;    -   (c) contact paste; and    -   (d) phase change material;    -   wherein    -   the thermal enhancement plate comprises a thermally conductive        electrically insulating solid material;    -   the contact paste comprises a one-part, pliable, non-curable,        thermally conductive material that has low electrical        conductivity;    -   the contact paste is placed between and contacts the heat source        PCB and the thermal enhancement plate;    -   the contact paste creates a low thermal impedance conduction        path from the heat source PCB to the thermal enhancement plate;    -   the phase change material is placed between and contacts the        thermal enhancement plate and a heat sink PCB;    -   the phase change material creates a low thermal impedance        conduction path from the thermal enhancement plate to the heat        sink PCB; and    -   the thermal enhancement plate, when making contact with the        thermal paste and the phase change material, creates a low        thermal impedance conduction path from the heat source PCB to        the heat sink PCB.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Thermal Enhancement Plate Alternative System Summary

The present invention as embodied in a thermal enhancement plateassembly alternative system anticipates a wide variety of variations inthe basic theme of construction but can be generalized as a thermalmanagement system comprising:

-   -   (a) heat source PCB;    -   (b) thermal enhancement plate; and    -   (c) contact paste;    -   wherein    -   the thermal enhancement plate comprises a thermally conductive        solid material;    -   the contact paste comprises a one-part, pliable, non-curable,        thermally conductive material that has low electrical        conductivity;    -   the contact paste is placed between and contacts the heat source        PCB and the thermal enhancement plate;    -   the contact paste creates a low thermal impedance conduction        path from the heat source PCB to the thermal enhancement plate;        and    -   the thermal enhancement plate, when making contact with the        thermal paste and the surface of a heat sink PCB, creates a low        thermal impedance conduction path from the heat source PCB to        the heat sink PCB.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Thermal Enhancement Plate Phase Change System Summary

The present invention as embodied in a thermal enhancement plateassembly phase change alternative system anticipates a wide variety ofvariations in the basic theme of construction but can be generalized asa thermal management system comprising:

-   -   (a) heat source PCB; and    -   (b) phase change material;    -   wherein    -   the phase change material makes contact with the surface of a        heat sink PCB;    -   the phase change material makes contact with the surface of the        heat source PCB or components on the surface of the heat source        PCB; and    -   the phase change material creates a low thermal impedance        conduction path from the heat source PCB to the heat sink PCB.

This general system summary may be augmented by the various elementsdescribed herein to produce a wide variety of invention embodimentsconsistent with this overall design description.

Method Summary

The present invention method anticipates a wide variety of variations inthe basic theme of implementation but can be generalized as a thermalmanagement method, the method operating in conjunction with a thermalmanagement system comprising:

-   -   (a) support pin;    -   (b) spacer pad; and    -   (c) contact paste;    -   wherein    -   the support pin comprises metal;    -   the spacer pad comprises low electrical conductivity material;    -   the contact paste comprises a thermally conductive pliable        material that has low electrical conductivity;    -   the support pin comprises a cylindrical shaft further        comprising:        -   (a) top heat source PCB insertion shaft further comprising a            top registration chamfer;        -   (b) bottom heat sink PCB insertion shaft further comprising            a bottom registration chamfer; and        -   (c) center support shaft section further comprising:            -   top and bottom self-centering inclined peripheral edges,                and            -   one or more longitudinal gassing vents;    -   the top and bottom self-centering inclined peripheral edges of        the support pin, when making contact with the surface of a heat        source PCB and a heat sink PCB, create a low thermal impedance        conduction path from the heat source PCB to the heat sink PCB        through the support pin;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, create a low thermal        impedance conduction path from the heat source PCB to the heat        sink PCB through the bottom-side and the top-side components        through the spacer pad;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, fixes the minimum        distance between the bottom-side components attached to the heat        source PCB and the top-side components attached to the heat sink        PCB;    -   the spacer pad, when making contact with the bottom-side        components attached to the heat source PCB and the top-side        components attached to the heat sink PCB, sets the total height        of the heat source PCB above the heat sink PCB; and    -   the contact paste, when making contact with the top-side        components of the heat source PCB and the bottom surface of a        thermally conductive plate covering the heat source PCB, creates        a low thermal impedance conduction path from the top-side        components of the heat source PCB to the thermally conductive        plate covering the heat source PCB through the contact paste;    -   wherein the method comprises the steps of:    -   (1) inserting the bottom heat sink PCB insertion shaft into a        hole in the heat sink PCB;    -   (2) soldering the bottom heat sink PCB insertion shaft to an        electrical contact on the surface of the heat sink PCB.

This general method may be modified heavily depending on a number offactors with rearrangement and/or addition/deletion of steps anticipatedby the scope of the present invention. Integration of this and otherpreferred exemplary embodiment methods in conjunction with a variety ofpreferred exemplary embodiment systems described herein is anticipatedby the overall scope of the present invention.

System/Method Variations

The present invention anticipates a wide variety of variations in thebasic theme of construction. The examples presented previously do notrepresent the entire scope of possible usages. They are meant to cite afew of the almost limitless possibilities.

This basic system and method may be augmented with a variety ofancillary embodiments, including but not limited to:

-   -   An embodiment wherein the heat source PCB and the heat sink PCB        are attached via one or more of the support pins using a        soldering process selected from a group consisting of: reflow        soldering, wave soldering, and hand soldering.    -   An embodiment wherein the thermally conductive plate creates a        low thermal impedance conduction path from the heat source PCB        to the thermally conductive plate through a thermally conductive        fastener connecting the conductive plate to the heat source PCB.    -   An embodiment wherein the thermally conductive plate creates a        low thermal impedance conduction path from the heat source PCB        to the thermally conductive plate through a thermally conductive        fastener connecting the conductive plate to the heat source PCB.    -   An embodiment wherein the spacer pad, when making contact with        the bottom-side components attached to the heat source PCB and        the top-side components attached to the heat sink PCB, creates a        positive contact pressure thermal conduction path between the        bottom-side components attached to the heat source PCB and the        top-side components attached to the heat sink PCB.    -   An embodiment wherein the metal is selected from a group        consisting of: copper, copper alloy, C11000 copper alloy, C11000        half-hard copper alloy, tin-plated-copper,        tin-plated-copper-alloy, tin-over-nickel plated C11000 half-hard        copper alloy, gold-over-nickel plated C11000 half-hard copper        alloy, copper-tellurium alloy, and brass alloy.    -   An embodiment wherein the spacer pad is thermally conductive.    -   An embodiment wherein the spacer pad foam comprises adhesive        surfaces.    -   An embodiment wherein the one or more longitudinal gassing vents        extend the entire length of the cylindrical center support shaft        comprising the support pin.    -   An embodiment wherein the one or more longitudinal gassing vents        extend a portion of the length of the cylindrical center support        shaft comprising the support pin.    -   An embodiment wherein the one or more longitudinal gassing vents        are V-shaped.    -   An embodiment wherein the one or more longitudinal gassing vents        are V-shaped at an angle greater than zero (0) degrees and less        than or equal to 180 degrees with respect to the longitudinal        axis of the cylindrical shaft.    -   An embodiment wherein the one or more longitudinal gassing vents        are V-shaped and positioned at 90-degree angles surrounding the        periphery of the cylindrical shaft.    -   An embodiment wherein the one or more longitudinal gassing vents        are V-shaped and positioned at 120-degree angles surrounding the        periphery of the cylindrical shaft.    -   An embodiment wherein the one or more longitudinal gassing vents        are U-shaped.    -   An embodiment wherein the one or more longitudinal gassing vents        are U-shaped and positioned at 90-degree angles surrounding the        periphery of the cylindrical shaft.    -   An embodiment wherein the one or more longitudinal gassing vents        are U-shaped and positioned at 120-degree angles surrounding the        periphery of the cylindrical shaft.    -   An embodiment wherein the one or more longitudinal gassing vents        comprise a single longitudinal gassing vent.    -   An embodiment wherein the one or more longitudinal gassing vents        comprise two longitudinal gassing vents.    -   An embodiment wherein the one or more longitudinal gassing vents        comprise three longitudinal gassing vents.    -   An embodiment wherein the one or more longitudinal gassing vents        comprise four longitudinal gassing vents.    -   An embodiment wherein the top and bottom self-centering inclined        peripheral edges of the support pin comprise an angle between 30        and 60 degrees with respect to the longitudinal axis of the        support pin.    -   An embodiment wherein the top registration chamfer and the        bottom registration chamfer comprise an angle between 30 and 60        degrees with respect to the longitudinal axis of the support        pin.    -   An embodiment wherein the assembly distance between the heat        source PCB and the heat sink PCB is determined by the hole        diameter in the heat sink PCB in which the bottom heat sink PCB        insertion shaft rests.    -   An embodiment wherein the contact paste comprises BERGQUIST        COMPANY part number “LF2000” or equivalent.    -   An embodiment wherein the phase change material comprises        BERGQUIST COMPANY part number “HF300G” or equivalent.    -   An embodiment wherein the thermal enhancement plate comprises an        electrically insulating solid material.    -   An embodiment wherein the surface of the heat source PCB is        covered with an insulating material.    -   An embodiment wherein the thermal enhancement plate directly        contacts the surface of the heat sink PCB.    -   An embodiment wherein the phase change material contacts the        surface of the heat sink PCB and either the surface of the heat        source PCB or a component on the heat source PCB.

CONCLUSION

A thermal management system/method allowing efficient electrical/thermalattachment of heat sourcing PCBs to heat sinking PCBs usingreflow/wave/hand soldering is disclosed. The disclosed system/method mayincorporate a combination of support pins, spacer pads, and/or contactpaste that mechanically attaches a heat sourcing PCB (and its associatedcomponents) to a heat sinking PCB such that thermal conductivity betweenthe two PCBs can be optimized while simultaneously allowing controlledelectrical conductivity between the two PCBs. Controlled electricalisolation between the two PCBs is provided for using spacer pads thatmay also be thermally conductive. Contact paste incorporated in someembodiments permits enhanced conductivity paths between the heatsourcing PCB, a thermally conductive plate mounted over the heatsourcing PCB, and the heat sinking PCB. The use of self-centeringsupport pins incorporating out-gassing vents in some embodiments allowsreflow/wave/hand soldering as desired.

Although a preferred embodiment of the present invention has beenillustrated in the accompanying drawings and described in the foregoingDetailed Description, it will be understood that the invention is notlimited to the embodiments disclosed, but is capable of numerousrearrangements, modifications, and substitutions without departing fromthe spirit of the invention as set forth and defined by the followingclaims.

What is claimed is:
 1. A thermal management system comprising: (a) heatsource PCB; (b) thermal enhancement plate; and (c) contact paste;wherein said thermal enhancement plate comprises a thermally conductivesolid material; said contact paste is placed between and contacts saidheat source PCB and said thermal enhancement plate; said contact pastecreates a low thermal impedance conduction path from said heat sourcePCB to said thermal enhancement plate; and said thermal enhancementplate, when making contact with said thermal paste and the surface of aheat sink PCB, creates a low thermal impedance conduction path from saidheat source PCB to said heat sink PCB.
 2. A thermal management systemcomprising: (a) heat source PCB; (b) thermal enhancement plate; and (c)contact paste; wherein said thermal enhancement plate comprises athermally conductive solid material; said contact paste is placedbetween and contacts said heat source PCB or components on the surfaceof said heat source PCB and said thermal enhancement plate; said contactpaste creates a low thermal impedance conduction path from said heatsource PCB or components on the surface of said heat source PCB to saidthermal enhancement plate; and said thermal enhancement plate, whenmaking contact with said thermal paste and the surface of a heat sinkPCB, creates a low thermal impedance conduction path from said heatsource PCB to said heat sink PCB.
 3. The thermal management system ofclaim 2 wherein said contact paste comprises a thermally conductivematerial that has low electrical conductivity.
 4. The thermal managementsystem of claim 2 wherein said contact paste comprises a one-part,pliable, non-curable, thermally conductive material having lowelectrical conductivity.
 5. The thermal management system of claim 2wherein said contact paste comprises BERGQUIST COMPANY part number“LF2000” or equivalent.
 6. The thermal management system of claim 2wherein said contact paste comprises a thermally conductive liquidfilling material that sets when cured.
 7. The thermal management systemof claim 2 wherein said contact paste comprises BERGQUIST COMPANY partnumber Gap Filler 2000 “GF2000” or equivalent material supplied as atwo-component curing system that produces a soft elastomer having lowelectrical conductivity.
 8. The thermal management system of claim 2wherein said contact paste mechanically attaches said heat source PCB tosaid thermal enhancement plate.
 9. The thermal management system ofclaim 2 wherein said contact paste mechanically attaches said heatsource PCB to said heat sink PCB.
 10. The thermal management system ofclaim 2 wherein said thermal enhancement plate comprises an electricallyinsulating solid material.
 11. The thermal management system of claim 2wherein said thermal enhancement plate comprises an electricallyconducting solid material.
 12. The thermal management system of claim 2wherein said thermal enhancement plate comprises an electricallyconducting solid material electrically isolated with an insulatingcovering.
 13. The thermal management system of claim 2 wherein said heatsource PCB and said heat sink PCB are attached via one or more supportpins using a soldering process selected from a group consisting of:reflow soldering, wave soldering, and hand soldering.
 14. The thermalmanagement system of claim 2 wherein said heat source PCB and said heatsink PCB are attached via one or more support pins wherein: said one ormore support pins comprises metal; said one or more support pins eachcomprises a unitary solid cylindrical shaft further comprising: (a)solid top heat source PCB insertion shaft further comprising a topregistration chamfer; (b) solid bottom heat sink PCB insertion shaftfurther comprising a bottom registration chamfer; and (c) solid centersupport shaft section further comprising: top and bottom self-centeringinclined peripheral edges; and one or more longitudinal gassing ventsformed only on the outer surface of said solid center support shaft;said top heat source PCB insertion shaft and said bottom heat sink PCBinsertion shaft have cylindrical diameters less than the diameter ofsaid center support shaft section; said top heat source PCB insertionshaft, said bottom heat sink PCB insertion shaft, and said centersupport shaft section form a single solid unitary structure having novoids along their common cylindrical axis; said top and bottomself-centering inclined peripheral edges of each of said one or moresupport pins, when making soldered contact with the surface of said heatsource PCB and said heat sink PCB, create a low thermal impedanceconduction path from said heat source PCB to said heat sink PCB througheach of said one or more support pins and soldered connections on saidtop and bottom self-centering inclined peripheral edges of each of saidone or more support pins; and said one or more support pins areconfigured to float within plated-through holes present on said heatsource PCB and said heat sink PCB during a soldering process used toform said soldered contact.
 15. The thermal management system of claim 2further comprising phase change material wherein: said phase changematerial is placed between and contacts said thermal enhancement plateand said heat sink PCB; and said phase change material creates a lowthermal impedance conduction path from said thermal enhancement plate tosaid heat sink PCB.
 16. The thermal management system of claim 15wherein said phase change material comprises BERGQUIST COMPANY partnumber “HF300G” or equivalent.
 17. The thermal management system ofclaim 2 further comprising phase change material wherein: said phasechange material makes contact with the surface of said heat sink PCB;said phase change material makes contact with the surface of said heatsource PCB; and said phase change material creates a low thermalimpedance conduction path from said heat source PCB to said heat sinkPCB.
 18. The thermal management system of claim 2 further comprisingphase change material wherein: said phase change material makes contactwith the surface of said heat sink PCB; said phase change material makescontact with the surface of said heat source PCB or components on thesurface of said heat source PCB; and said phase change material createsa low thermal impedance conduction path from said heat source PCB orcomponents on the surface of said heat source PCB to said heat sink PCB.19. The thermal management system of claim 18 wherein said phase changematerial comprises BERGQUIST COMPANY part number “HF300G” or equivalent.20. The thermal management system of claim 18 wherein said heat sourcePCB and said heat sink PCB are attached via one or more support pinsusing a soldering process selected from a group consisting of: reflowsoldering, wave soldering, and hand soldering.
 21. The thermalmanagement system of claim 18 wherein said heat source PCB and said heatsink PCB are attached via one or more support pins wherein: said one ormore support pins comprises metal; said one or more support pins eachcomprises a unitary solid cylindrical shaft further comprising: (a)solid top heat source PCB insertion shaft further comprising a topregistration chamfer; (b) solid bottom heat sink PCB insertion shaftfurther comprising a bottom registration chamfer; and (c) solid centersupport shaft section further comprising: top and bottom self-centeringinclined peripheral edges; and one or more longitudinal gassing ventsformed only on the outer surface of said solid center support shaft;said top heat source PCB insertion shaft and said bottom heat sink PCBinsertion shaft have cylindrical diameters less than the diameter ofsaid center support shaft section; said top heat source PCB insertionshaft, said bottom heat sink PCB insertion shaft, and said centersupport shaft section form a single solid unitary structure having novoids along their common cylindrical axis; said top and bottomself-centering inclined peripheral edges of each of said one or moresupport pins, when making soldered contact with the surface of said heatsource PCB and said heat sink PCB, create a low thermal impedanceconduction path from said heat source PCB to said heat sink PCB througheach of said one or more support pins and soldered connections on saidtop and bottom self-centering inclined peripheral edges of each of saidone or more support pins; and said one or more support pins areconfigured to float within plated-through holes present on said heatsource PCB and said heat sink PCB during a soldering process used toform said soldered contact.